Adhesive composition for high-power optical fiber

ABSTRACT

An object of the present invention is to provide an adhesive composition for a high-power optical fiber having a low pull-in amount. The adhesive composition for a high-power optical fiber of the present invention contains: a compound (A) having an aromatic ring and a reactive silicon-containing group; a glycidyl compound (B); and a compound (C) having a silsesquioxane cage structure.

TECHNICAL FIELD

The present invention relates to an adhesive composition for ahigh-power optical fiber.

BACKGROUND ART

In recent years, due to the expansion of the internet, technologies toincrease communication capability have become increasingly important,and optical fiber network has been expanded. In joining technologiesused for fabrication of optical materials and optical elements used insuch optical communication system, it is popular to connect an opticalfiber using a connector (e.g., SC connector), and an adhesivecomposition is used to fix the optical fiber to the ferrule in theconnector.

For example, Patent Document 1 discloses “an adhesive compositioncomprising an epoxysilane obtained by reacting an epoxy resin with animino group-containing silane coupling agent, and a particular imidazolecompound” (claim 1).

Meanwhile, when light is transmitted through an optical fiber, some ofthe light may be absorbed into a component and converted to thermalenergy, thereby increasing the temperature of the component.Furthermore, when the temperature of the component is increased, theoptical fiber may be pulled in within the connector due to thedifference between coefficients of linear thermal expansion ofcomponents. When such pull-in of the optical fiber occurs, a gap iscreated at the edge of the optical fiber, thereby increasing reflectionattenuation.

Therefore, the adhesive composition is required to maintain the ferruleand the optical fiber at a high level and less likely to cause pull-ineven when light is transmitted therethrough.

CITATION LIST Patent Literature

Patent Document 1: Japanese Unexamined Patent Application PublicationNo. 2007-191667A

SUMMARY OF INVENTION Technical Problem

Recently, output of optical transmission has been increased (power hasbeen increased) in response to demand for ultralong distancetransmission or wavelength multiplex transmission, adhesive compositionsused in connectors are required to have functions to maintain an opticalfiber in a ferrule at even higher level.

In such circumstances, the inventors of the present invention produced aconnector by preparing an adhesive composition using Patent Document 1as a reference, and joining an optical fiber and a ferrule using thecomposition. Using the obtained connector, continuous wave operation wasperformed at a high power (approximately 1 W). As a result, it was foundthat the pull-in amount after the continuous wave operation did notsatisfy the level required these days.

Therefore, in light of the circumstances described above, an object ofthe present invention is to provide an adhesive composition for ahigh-power optical fiber that can produce a connector having a lowpull-in amount even when the connector is used for high powerapplications.

Solution to Problem

As a result of diligent research to solve the problems described above,the inventors of the present invention have found that a connectorhaving a low pull-in amount even when the connector is used for highpower applications can be produced by blending a compound having asilsesquioxane cage structure. Specifically, the inventors discoveredthat the object described above can be achieved by the followingfeatures.

(1) An adhesive composition for a high-power optical fiber comprising: acompound (A) having an aromatic ring and a reactive silicon-containinggroup; a glycidyl compound (B); and a compound (C) having asilsesquioxane cage structure.

(2) The adhesive composition for a high-power optical fiber according to(1) above, further comprising an imidazole compound (D).

(3) The adhesive composition for a high-power optical fiber according to(1) or (2) above, where the reactive silicon-containing group is ahydrolyzable silicon-containing group.

(4) The adhesive composition for a high-power optical fiber according toany one of (1) to (3) above, where the compound (A) is obtained byreacting an epoxy compound (e) with a compound (f) having a reactivegroup that reacts with the epoxy group contained in the epoxy compound(e).

(5) The adhesive composition for a high-power optical fiber according to(4) above, where

the epoxy compound (e) is an aromatic epoxy compound, and

the compound (f) is an iminosilane compound.

(6) The adhesive composition for a high-power optical fiber according to(4) above, where

the epoxy compound (e) is an epoxysilane compound, and

the compound (f) is an aromatic amine compound.

(7) The adhesive composition for a high-power optical fiber according toany one of (4) to (6) above, where

the compound (f) contains an amino group or an imino group, and

the number of equivalent of active hydrogen in the amino group or theimino group is from 0.1 to 1.0 equivalent relative to the amount ofepoxy group contained in the epoxy compound (e).

(8) The adhesive composition for a high-power optical fiber according toany one of (1) to (7) above, where the compound (C) is obtained bysubjecting at least one type of silane selected from the groupconsisting of epoxysilane, aminosilane, vinylsilane, methacrylsilane,acrylsilane, and mercaptosilane to condensation.

(9) The adhesive composition for a high-power optical fiber according toany one of (1) to (8) above, where

a proportion (A/(A+B+C)) of a content of the compound (A) in a totalcontent (A+B+C) of the content of the compound (A), a content of theglycidyl compound (B), and a content of the compound (C) is from 20 to70 mass %;

a proportion (B/(A+B+C)) of the content of the glycidyl compound (B) inthe total content (A+B+C) is from 20 to 70 mass %; and

a proportion (C/(A+B+C)) of the content of the compound (C) in the totalcontent (A+B+C) is from 5 to 40 mass %.

Advantageous Effects of Invention

As described below, the present invention can provide an adhesivecomposition for a high-power optical fiber that can produce a connectorhaving a low pull-in amount even when the connector is used for highpower applications.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view of an embodiment of a connectorproduced using the adhesive composition for a high-power optical fiberof the present invention.

FIG. 2 is a GPC chromatogram of the compound C1 (silsesquioxane cage(mixture)).

DESCRIPTION OF EMBODIMENTS

The adhesive composition for a high-power optical fiber of the presentinvention will be described below.

In this specification, a numerical range represented using “(from) . . .to . . . ” refers to a range including the numerical values statedbefore and after the “ . . . to . . . ” as an upper limit value and alower limit value.

Furthermore, in this specification, “(meth)acryl group” refers to “acrylgroup” or “methacryl group”.

Adhesive Composition for High-power Optical Fiber

The adhesive composition for a high-power optical fiber of the presentinvention (hereinafter, also simply referred to as “composition of thepresent invention”) contains: a compound (A) having an aromatic ring anda reactive silicon-containing group; a glycidyl compound (B); and acompound (C) having a silsesquioxane cage structure.

Since the composition of the present invention has such constitution, itis conceived that the pull-in amount is low even when the composition isused for high power applications. Although the reason is not clear, itis assumed to be as follows.

Since the composition of the present invention contains the compound (A)having an aromatic ring and a reactive silicon-containing group and theglycidyl compound (B) as described above, the compound (A) and thecompound (B) are bonded due to heating or the like to form athree-dimensional crosslinked structure. Therefore, it is conceivedthat, since the composition of the present invention contains thecompound (C) having a silsesquioxane cage structure as described above,an adhesive layer having a structure in which the rigid silsesquioxanecage structures are uniformly arranged in the crosslinked structure isformed due to high affinity between the silsesquioxane cage structureand the silicon-containing structure derived from the reactivesilicon-containing group within the crosslinked structure.

The adhesive layer formed from the composition of the present inventionis thus thought to have a significantly excellent balance between heatresistance and adhesive strength. That is, the glass transitiontemperature (Tg) is increased due to the introduction of the rigidsilsesquioxane cage structures, thereby enhancing the heat resistance.Meanwhile, it is conceived that the adhesive strength is maintained at ahigh level since the silsesquioxane cage structures are uniformlyarranged. As a result, it is conceived that the connector produced usingthe composition of the present invention hardly causes pull-in even whenhigh power optical transmission is performed.

This is also inferred from the fact that, for cases where the adhesivecomposition contains no compound (C) having a silsesquioxane cagestructure (comparative examples), the pull-in amount is greater comparedto the cases where the composition contains a compound (C) having asilsesquioxane cage structure (working examples) as shown in workingexamples and comparative examples described below.

Each component contained in the composition of the present inventionwill be described in detail hereinafter.

Compound (A) Having Aromatic Ring and Reactive Silicon-containing Group

The compound (A) contained in the composition of the present inventionis not particularly limited as long as the compound (A) is a compoundhaving at least one aromatic ring and at least one reactivesilicon-containing group.

The aromatic ring is not particularly limited; however, the aromaticring is preferably an aromatic ring having from 6 to 20 carbon atoms.

Specific examples of the aromatic ring include a benzene ring,naphthalene ring, anthracene ring, phenanthrene ring, fluorene ring,triphenylene ring, naphthacene ring, biphenyl ring (the two phenylgroups may be bonded in any bonding form), and terphenyl ring (the threebenzene rings may be bonded in any bonding form). Among these, a benzenering is preferable.

The reactive silicon-containing group is a silicon-containing group thathas from 1 to 3 reactive groups bonded to a silicon atom and that canform crosslink(s) by causing a reaction in the presence of moisture or acrosslinking agent or the like or, as necessary, by using a catalyst orthe like. Specific examples thereof include a silicon halide-containinggroup, silicon hydride-containing group, hydrolyzable silicon-containinggroup, and the like. Among these, a hydrolyzable silicon-containinggroup is preferable.

The silicon halide-containing group described above has 1 to 3 halogengroups bonded to a silicon atom, and specific examples thereof include achlorodimethylsilyl group, dichloromethylsilyl group, and trichlorosilylgroup.

The silicon hydride-containing group described above has 1 to 3 hydrogenatoms bonded to a silicon atom, and specific examples thereof include ahydrodimethylsilyl group, dihydromethylsilyl group, and trihydrosilylgroup.

The silicon halide-containing group can, for example, form a bond tocrosslink by causing a dehydrohalogenation reaction with the siliconhydride-containing group described above. Furthermore, the siliconhalide-containing group can form a silicon-carbon bond to crosslink, bycausing a metathesis reaction with a Grignard reagent and then causing ametal dehalogenation reaction. Furthermore, when an alkali metal ormagnesium is used, the silicon halide-containing group can form asilicon-carbon bond to crosslink, by causing a reductive silylationreaction with an aromatic hydrocarbon, conjugated diene, aromaticaldehyde, ketone, carboxylic acid, ester, or imine

The silicon hydride-containing group can, for example, form a bond tocrosslink by causing a dehydrohalogenation reaction with the siliconhalide-containing group described above. Furthermore, the siliconhydride-containing group can form a silicon-carbon bond to crosslink bycausing a hydrosilylation reaction with a compound having an unsaturatedcarbon bond.

The hydrolyzable silicon-containing group is a silicon-containing groupthat has 1 to 3 hydroxyl groups and/or hydrolyzable group bonded to asilicon atom, and that, in the presence of moisture or a crosslinkingagent and with the use of a catalyst or the like as necessary, iscapable of crosslinking by causing a condensation reaction and thusforming siloxane bonds. Examples of such groups include alkoxysilylgroups, alkenyloxysilyl groups, acyloxysilyl groups, aminosilyl groups,aminoxysilyl groups, oximesilyl groups, and amidosilyl groups.Specifically, alkoxysilyl groups, alkenyloxysilyl groups, acyloxysilylgroups, aminosilyl groups, aminoxysilyl groups, oximesilyl groups,amidosilyl groups, and the like represented by formulas below arepreferably used.

Among these, alkoxysilyl groups are preferred from the standpoint ofease of handleability.

The alkoxy group bonded to the silicon atom on the alkoxysilyl group isnot particularly limited, but the alkoxy group is preferably a methoxygroup, an ethoxy group, or a propoxy group because raw materials forsuch are readily available.

Groups other than the alkoxy group bonded to the silicon atom on thealkoxysilyl group are not subjected to any particular limitation,although preferred examples include hydrogen atoms, and alkyl groups,alkenyl groups, and arylalkyl groups that have 20 carbon atoms or less,such as methyl groups, ethyl groups, propyl groups, and isopropylgroups.

Preferred Embodiment

The compound (A) is preferably a compound obtained by reacting an epoxycompound (e) with a compound (f) having a reactive group that reactswith the epoxy group contained in the epoxy compound (e).

The epoxy compound (e) is not particularly limited as long as the epoxycompound (e) is a compound having at least one epoxy group.

Specific examples of the epoxy compound (e) include glycidyl ether typeobtained by reacting epichlorohydrin with a polyhydric phenol, such asbisphenol A, bisphenol F, bisphenol S, hexahydrobisphenol A,tetramethylbisphenol A, pyrocatechol, resorcinol, cresol novolac,tetrabromobisphenol A, trihydroxybiphenyl, bisresorcinol, bisphenolhexafluoroacetone, tetramethylbisphenol F, bixylenol, anddihydroxynaphthalene; polyglycidyl ether type obtained by reactingepichlorohydrin with an aliphatic polyhydric alcohol, such as glycerin,neopentyl glycol, ethylene glycol, propylene glycol, butylene glycol,hexylene glycol, polyethylene glycol, and polypropylene glycol; glycidylether ester type obtained by reacting epichlorohydrin with ahydroxycarboxylic acid, such as p-oxybenzoic acid and β-oxynaphthoicacid; polyglycidyl ester type derived from polycarboxylic acids, such asphthalic acid, methylphthalic acid, isophthalic acid, terephthalic acid,tetrahydrophthalic acid, hexahydrophthalic acid, endomethylenetetrahydrophthalic acid, endomethylene hexahydrophthalic acid,trimellitic acid, and polymerized fatty acids; glycidylaminoglycidylether type derived from aminophenols and aminoalkylphenols;glycidylaminoglycidyl ester type derived from aminobenzoic acids;glycidylamine type derived from aniline, toluidine, tribromoaniline,xylylenediamine, diamino cyclohexane, bisaminomethylcyclohexane,4,4′-diaminodiphenyl methane, and 4,4′-diaminodiphenyl sulfone;epoxidized polyolefin, glycidylhydantoin, glycidylalkylhydantoin,triglycidyl cyanurate, and the like; monoepoxy compounds, such as butylglycidyl ether, phenyl glycidyl ether, alkyl phenyl glycidyl ether,glycidyl benzoate, and styrene oxide; and the like. One type or amixture of two or more types of these can be used.

The epoxy compound (e) is preferably an aromatic epoxy compound or anepoxy silane compound, and is more preferably an aromatic epoxycompound.

The aromatic epoxy compound is not particularly limited as long as thearomatic epoxy compound is an epoxy compound having at least onearomatic ring. Specific examples and preferred form of the aromatic ringare the same as those of the aromatic ring contained in the compound (A)described above.

The compound (f) is not particularly limited as long as the compound (f)is a compound having at least one reactive group that reacts with theepoxy group contained in the epoxy compound (e).

Specific examples of the reactive group that reacts with the epoxy groupcontained in the epoxy compound (e) include amino groups, imino groups,ureide groups, mercapto groups, and acid anhydride groups.

Specific examples of the compound (f) include aminosilane compounds,such as γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane,γ-aminopropylmethyldimethoxysilane, γ-aminopropylethyldiethoxysilane,bistrimethoxysilylpropylamine, bistriethoxysilylpropylamine,bismethoxydimethoxysilylpropylamine, bisethoxydiethoxysilylpropylamine,N-β(aminoethyl)γ-aminopropyltrimethoxysilane,N-β(aminoethyl)γ-aminopropylmethyldimethoxysilane,N-β(aminoethyl)γ-aminopropyltriethoxysilane,N-β(aminoethyl)γ-aminopropylethyldiethoxysilane,3,3-dimethyl-4-aminobutyltrimethoxysilane,3,3-dimethyl-4-aminobutylmethyldimethoxysilane; iminosilane compounds,such as (N-cyclohexylaminomethyl)methyldiethoxysilane,(N-cyclohexylaminomethyl)triethoxysilane,(N-phenylaminomethyl)methyldimethoxysilane,(N-phenylaminomethyl)trimethyloxysilane, compounds represented byFormula (1) below and N-phenyl-3-aminopropyltrimethoxysilane representedby Formula (2) below:

ureide silane compounds, such as γ-ureidepropyltrimethoxysilane;mercapto silane compounds, such as γ-mercaptopropyltrimethoxysilane,γ-mercaptopropyltriethoxysilane, γ-mercaptopropylmethyldimethoxysilane,and γ-mercaptopropylmethyldiethoxysilane.

These may be used alone, or two or more types may be used incombination.

The compound (f) described above is preferably a compound having anamino group (—NH₂) or an imino group (═NH, —NH—). Among these, thecompound (f) is preferably an iminosilane compound or an aromatic aminecompound, and is more preferably an iminosilane compound.

The iminosilane compound is not particularly limited as long as theiminosilane compound is a silane compound having an imino group.Specific examples of the iminosilane compound are as described above.

When the compound (f) has an amino group or an imino group, the numberof equivalent of active hydrogen in the amino group or the imino groupcontained in the compound (f) (when the compound (f) has both an aminogroup and an imino group, the total number of equivalent of the aminogroup and the imino group) is preferably from 0.1 to 1.0 equivalentrelative to the amount of epoxy group contained in the epoxy compound(e), and more preferably 0.6 equivalent or greater since the pull-inamount will be low.

Glycidyl Compound (B)

The glycidyl compound (B) contained in the composition of the presentinvention is not particularly limited as long as the glycidyl compound(B) is a compound having at least one glycidyl group.

Specific examples of the glycidyl compound (B) include compounds havingat least one glycidyl group described as the specific examples of theepoxy compound (e) described above. Among these, a glycidylaminoglycidylether type is preferable.

The glycidyl compound (B) preferably has no reactive silicon-containinggroup.

Compound (C) Having Silsesquioxane Cage Structure

The compound (C) contained in the composition of the present inventionis not particularly limited as long as at least a part of the compoundhas a silsesquioxane cage structure. Note that “silsesquioxane cagestructure” is a silsesquioxane structure having a cage-like skeleton.Furthermore, “silsesquioxane structure” is a structure formed fromrepeating units: RSiO_(1.5) (R: hydrogen atom or substituent).

The silsesquioxane cage structure may be a complete silsesquioxane cagestructure or an incomplete silsesquioxane cage structure; however, thesilsesquioxane cage structure is preferably a complete silsesquioxanecage structure.

A part of the compound (C) may have a random or ladder typesilsesquioxane structure.

The compound (C) is preferably cage-type silsesquioxane, and especially,the compound (C) is preferably a compound represented by any one ofFormulas (B-1) to (B-3) below.

In the Formulas (B-1) to (B-3), R represents a hydrogen atom or asubstituent. Note that the plurality of R moieties may be the same ordifferent.

The substituent is not particularly limited as long as the substituentis a monovalent substituent. Specific examples thereof includehydrocarbon groups that may have a halogen atom, hydroxy group, nitrogroup, carboxy group, alkoxy group, amino group, mercapto group, acylgroup, imide group, phosphino group, phosphinyl group, silyl group, orhetero atom, (meth)acryl group-containing groups, and epoxygroup-containing groups. Among these, an epoxy group-containing group(preferably a glycidyl group- (—CH₂-A, A: epoxy group) containing group,and more preferably a glycidoxy group- (—O—B, B: glycidyl group)containing group) is preferable.

Examples of the halogen atom include a fluorine atom, chlorine atom,bromine atom, and iodine atom.

Examples of the hetero atom of the hydrocarbon group that may have ahetero atom include an oxygen atom, nitrogen atom, sulfur atom, andphosphorous atom.

Examples of the hydrocarbon group that may have a hetero atom includealiphatic hydrocarbon groups, aromatic hydrocarbon groups, and groupsthat have a combination of these.

The aliphatic hydrocarbon group may be in a form of straight-chain,branched-chain, or ring. Specific examples of the aliphatic hydrocarbongroup include straight-chain or branched alkyl groups (especially, thosehaving from 1 to 30 carbon atoms), straight-chain or branched alkenylgroups (especially, those having from 2 to 30 carbon atoms), andstraight-chain or branched alkynyl groups (especially, those having from2 to 30 carbon atoms).

Examples of the aromatic hydrocarbon group include aryl groups, andnaphthyl groups. Examples of the aryl group include aryl groups havingform 6 to 18 carbon atoms, such as a phenyl group, tolyl group, andxylyl group.

R in the Formulas (B-1) to (B-3) is preferably a group represented byFormula (X) below.[Chemical Formula 6]R_(x)-L₁-*  Formula (X)

In Formula (X) above, R_(x) represents an epoxy group, glycidyl group,amino group, vinyl group, (meth)acryl group, or mercapto group.

In Formula (X) above, L₁ represents a single bond or a divalent organicgroup.

Examples of the divalent organic group include divalent aliphatichydrocarbon groups (e.g. alkylene group, preferably having from 1 to 8carbon atoms), divalent aromatic hydrocarbon groups (e.g. arylene group,preferably having from 6 to 12 carbon atoms), —O—, —S—, —SO₂—, —NR— (R:hydrocarbon group), —SiR₁R₂— (R₁ and R₂: hydrocarbon group), —CO—, —NH—,—COO—, —CONH—, and groups that have a combination of these (e.g.alkyleneoxy groups, alkyleneoxycarbonyl groups, and alkylenecarbonyloxygroups). Among these, alkylene groups, —O—, —S—, —NR—, or groups thathave a combination of these are preferable.

In Formula (X) above, * indicates a bonding position.

The proportion of the compound that is represented by any one ofFormulas (B-1) to (B-3) above is preferably 50 mass % or greater, andmore preferably 70 mass % or greater, in the compound (C).

The compound (C) is preferably a compound obtained by subjecting atleast one type of silane selected from the group consisting ofepoxysilane, aminosilane, vinylsilane, methacrylsilane, acrylsilane, andmercaptosilane to condensation.

Among these, the compound (C) is more preferably a compound obtained bysubjecting silane represented by Formula (3) below to condensation.

The definition, specific examples, and preferred forms of X in Formula(3) above are the same as those of the group represented by Formula (X)above.

In Formula (3) above, R₃₁ represents a hydrolyzable group.

The hydrolyzable group is not particularly limited; however, examplesthereof include alkoxy groups, phenoxy groups, carboxyl groups, andalkenyloxy groups. Among these, alkoxy groups are preferable. When thehydrolyzable group is an alkoxy group, the number of carbon atoms of thealkoxy group is preferably from 1 to 16, and more preferably from 1 to4. Examples of the alkoxy group having from 1 to 4 carbon atoms includea methoxy group, ethoxy group, and propoxy group.

The proportion (A/(A+B+C)) of the content of the compound (A) in a totalcontent (A+B+C) of the content of the compound (A), the content of theglycidyl compound (B), and the content of the compound (C) is preferablyfrom 20 to 70 mass %, and more preferably from 30 to 50 mass %.

The proportion (B/(A+B+C)) of the content of the glycidyl compound (B)in the total content (A+B+C) is preferably from 20 to 70 mass %, andmore preferably from 40 to 60 mass %.

The proportion (C/(A+B+C)) of the content of the compound (C) in thetotal content (A+B+C) is preferably from 5 to 40 mass %, more preferablyfrom 5 to 25 mass %, even more preferably 7 mass % or greater, andparticularly preferably 10 mass % or greater.

The proportion (A/(A+B+C)) of the content of the compound (A) in thetotal content (A+B+C) of 20 to 70 mass %, the proportion (B/(A+B+C)) ofthe content of the glycidyl compound (B) in the total content (A+B+C) of20 to 70 mass %, and the proportion (C/(A+B+C)) of the content of thecompound (C) in the total content (A+B+C) of 5 to 40 mass % arepreferable. In particular, the proportion (A/(A+B+C)) of the content ofthe compound (A) in the total content (A+B+C) of 30 to 50 mass %, theproportion (B/(A+B+C)) of the content of the glycidyl compound (B) inthe total content (A+B+C) of 40 to 60 mass %, and the proportion(C/(A+B+C)) of the content of the compound (C) in the total content(A+B+C) of 5 to 25 mass % are more preferable.

Optional Component

The composition of the present invention may further contain additiveswithin a scope that does not inhibit the effect or purpose thereof.

Examples of the additive include curing agents, fillers, reactionretarders, antiaging agents, antioxidants, pigments (dyes),plasticizers, thixotropic agents, UV absorbents, flame retardants,solvents, surfactants (including leveling agents), dispersants,dehydrating agents, adhesion imparting agents, antistatic agents, andsilane coupling agents excluding (A) to (C) described above.

Imidazole Compound (D)

The composition of the present invention preferably contains animidazole compound (D). The imidazole compound (D) functions mainly as acuring agent.

The imidazole compound (D) is not particularly limited as long as theimidazole compound (D) is imidazole or an imidazole compound (e.g.imidazole derivative).

The imidazole compound (D) is preferably a compound represented byFormula (4) below.

In Formula (4) above, R₄₁ to R₄₃ each independently represent a hydrogenatom or a substituent. The definition, specific examples, and preferredforms of the substituent are the same as those of R in Formulas (B-1) to(B-3) described above. R₄₃ is preferably an alkyl group (preferablyhaving from 1 to 30 carbon atoms).

The content of the imidazole compound (D) is not particularly limited;however, the proportion of the content of the imidazole compound (D) inthe total content (A+B+C) is preferably from 1 to 20 mass %, and morepreferably from 5 to 15 mass %.

Method of Producing Composition of Present Invention

The method of producing the composition of the present invention is notparticularly limited, and an example thereof is a method that uniformlymixes each of the components described above using conventionally knowndevices. Note that, when the composition of the present inventioncontains a curing agent such as an imidazole compound, it is preferableto mix the components other than the curing agent and then mix thecuring agent.

Method of Curing Composition of Present Invention

The method of curing the composition of the present invention is notparticularly limited, and examples thereof include a method of heatingthe composition at 100 to 200° C. for 10 minutes to 5 hours, and thelike.

Use

Since the composition of the present invention has a low pull-in amount,the composition is useful as an adhesive composition for an opticalfiber. Furthermore, as described above, since the composition of thepresent invention has a low pull-in amount even when used for high powerapplications (100 mW or greater, preferably 1 W or greater), thecomposition is particularly useful as an adhesive composition for ahigh-power optical fiber. For example, the composition of the presentinvention is useful as an adhesive composition for an optical fiber thatis required for high power transmission, such as ultralong distancetransmission or wavelength multiplex transmission.

Connector

An embodiment of a connector produced by using the composition of thepresent invention will be described below with reference to the drawing.

FIG. 1 is a cross-sectional view of an embodiment of a connectorproduced using the adhesive composition of the present invention.

The connector 10 is a connector formed by removing a polymer coatinglayer of an edge portion of an optical fiber 1 having a core part 2, acladding part 3, and a polymer coating layer 4; coating the compositionof the present invention described above on the part where the polymercoating layer has been removed; inserting it to a cavity portion of aferrule 7 that is fixed on a flange 8; and heating the assembly toadhere the optical fiber 1 and the ferrule 7 by sandwiching an adhesivelayer 6 (cured product of the composition of the present invention)therebetween.

EXAMPLES

Hereinafter, the present invention will be further described in detailwith reference to examples; however, the present invention is notlimited thereto.

Synthesis of Compound (A)

Components shown in Table 1 below were mixed at compositions (part bymass) shown in the same table and stirred in an inert gas atmosphere at120° C. for 8 hours to obtain compounds A1, A2, A3, A4, A5, and A6,which were the compound (A) having an aromatic ring and a reactivesilicon-containing group.

TABLE 1 Compound Compound Compound Compound Compound Compound A1 A2 A3A4 A5 A6 Epoxy 100 100 compound e1 Epoxy 100 100 compound e2 Epoxy 238358 compound e3 Iminosilane 64 70 96 105 compound f1 Amine 100 100compound f2 Number of 0.5 0.5 0.5 0.75 0.75 0.75 equivalent (equivalent)

The components listed in Table 1 are described below.

-   -   Epoxy compound e1: Epotohto YDF-128 (bisphenol A diglycidyl        ether, manufactured by Tohto Kasei Co., Ltd.) (The structure is        illustrated below)

-   -   Epoxy compound e2: Epotohto YDF-170 (bisphenol F diglycidyl        ether, manufactured by Tohto Kasei Co., Ltd.) (The structure is        illustrated below)

-   -   Epoxy compound e3: 3-glycidoxypropyltrimethoxysilane (A-187,        manufactured by Momentive Performance Materials Inc.) (The        structure is illustrated below)

-   -   Iminosilane compound f1: Alink-15        (N-ethyl-3-aminoisobutyltrimethoxysilane, manufactured by Dow        Corning Toray Co., Ltd.) (The structure is illustrated below)

-   -   Amine compound f2: methylenedianiline (MDA, manufactured by        Kanto Chemical Co., Ltd.) (The structure is illustrated below)

In Table 1, the number of equivalent indicates the number of equivalent(equivalent) of active hydrogen in the amino group or the imino groupcontained in the iminosilane compound f1 or the amine compound f2relative to the amount of the epoxy group contained in the epoxycompounds e1 to e3.

Note that, when one molecule of the epoxy compound e1 and one moleculeof the iminosilane compound f1 are reacted, the following compound canbe obtained.

Furthermore, when one molecule of the epoxy compound e2 and one moleculeof the iminosilane compound f1 are reacted, the following compound canbe obtained.

Furthermore, when one molecule of the epoxy compound e3 and one moleculeof the amine compound f2 are reacted, the following compound can beobtained.

Synthesis of Compound C1

In a reaction vessel equipped with a stirrer, a dropping funnel, and athermometer, 50 mL of isopropanol (IPA) as a solvent and 4.0 g of 5%tetramethylammonium hydroxide (TMAH) aqueous solution as a basiccatalyst were loaded. In a dropping funnel, 15 mL of IPA and 23.36 g of3-glycidoxypropyltrimethoxysilane were charged, and while the content ofthe reaction vessel was being stirred, the IPA solution of3-glycidoxypropyltrimethoxysilane was added dropwise at room temperatureover 30 minutes. After the completion of the dropwise addition, themixture was stirred for 6 hours without being heated. After the 6 hoursof stirring, the IPA (solvent) was removed under reduced pressure, andthe obtained substance was dissolved in toluene. After this solution waswashed with saturated saline until the solution became neutral, thesolution was dehydrated with anhydrous magnesium sulfate. The anhydrousmagnesium sulfate was then filtered out, and the obtained substance wascondensed to obtain a hydrolysis product (silsesquioxane).

Thereafter, in a reaction vessel equipped with a stirrer, a Dean-Starkapparatus, and a condenser tube, the silsesquioxane obtained asdescribed above, 50 mL of toluene, and 2.1 g of 10% TMAH aqueoussolution were loaded and gradually heated to distill off water.Furthermore, the mixture was heated to 120° C., and recondensationreaction was performed again at the reflux temperature of toluene. Atthis time, the temperature of the reaction solution was 108° C. Afterthe reflux using toluene, the obtained substance was stirred for 2hours, and then the reaction was terminated. After the reaction solutionwas washed with saturated saline until the reaction solution becameneutral, the reaction solution was dehydrated with anhydrous magnesiumsulfate. The anhydrous magnesium sulfate was then filtered out, and theobtained substance was condensed to obtain 15.65 g of cage-typesilsesquioxane (mixture), which was the target product. The obtainedcage-type silsesquioxane (mixture) was a colorless viscous liquid thatwas soluble in various organic solvents. The obtained cage-typesilsesquioxane (mixture) was used as the compound C1.

For the compound C1, the content of the cage-type silsesquioxane wasdetermined by GPC analysis and NMR analysis, and the content was 71 mass%. Specifically, the content was determined as described below.

First, GPC analysis was conducted for the compound C1 in the followingconditions. FIG. 2 shows a GPC chromatogram. Furthermore, the molecularweight of each peak (based on polypropylene glycol (PPG)), distribution,and area of the GPC are shown below. Each peak (peaks 1 to 3) of the GPCwas isolated and identified by NMR. The peaks 2 and 3 were peaksoriginated from cage-type silsesquioxane. The content (mass %) of thecage-type silsesquioxane in the compound C1 was determined from theproportion of the total area (71) of the peaks 2 and 3 relative to thetotal area (100) of the peaks 1 to 3.

Conditions of GPC Analysis

-   -   Instrument: GPC system, manufactured by Shimadzu Corporation    -   System controller: CBM-20A    -   Column oven: CTO-20A    -   Online degassing unit: DGU-20A3    -   Liquid delivery pump: LC-20AD    -   Autosampler: SIL-20AHT    -   Eluent: THF    -   Detector: RI detector

TABLE 2 Mn Mw Mz Mw/Mn Mz/Mw % Total 1601 2368 4116 1.47864 1.73825 100Peak 1 3995 4740 5968 1.18664 1.25906 29.1408 Peak 2 2022 2047 20731.01248 1.01234 17.8696 Peak 3 1144 1171 1198 1.02374 1.02277 52.9896Preparation of Adhesive Composition

Components of liquid A shown in Table 2 below were mixed at compositions(part by mass) shown in the same table and stirred with a stirrer.Thereafter, components of liquid B shown in the same table were addedand stirred with a stirrer to prepare an adhesive composition of each ofworking examples and comparative examples.

Note that, for the compound C1, the values written on the upper row arethe amounts (part by mass) of cage-type silsesquioxane (mixture), andthe values written on the lower row (values written in parentheses) arethe net amounts (part by mass) of the cage-type silsesquioxane containedin the cage-type silsesquioxane (mixture).

Evaluation of Pull-in Amount

An SC connector having a form illustrated in FIG. 1 (using a fixedattenuator (5 to 20 dB) that is not illustrated) was produced using theprepared adhesive composition. An adhesive layer was formed as describedbelow. For a single-mode optical fiber having a core part, a claddingpart, and a polymer coating layer, a length of 2 cm of the polymercoating layer located at the edge portion of the single-mode opticalfiber was removed. The prepared adhesive composition was coated on theportion where the polymer coating layer was removed. The optical fibercoated with the adhesive composition was then inserted to a cavityportion of a zirconia ferrule through the edge of a plug, and heated at130° C. for 3 hours to cure, thereby forming an adhesive layer.

The pull-in amount of the optical fiber when continuous wave operationwas performed at 1 W for 40 minutes using an LD light (wavelength: 1.55μm) was measured with the obtained SC connector. The results are shownin Table 2. Practically, the pull-in amount is preferably 50 nm orlower.

TABLE 3 Working Working Working Working Working Working Working ExampleExample Example Example Example Example Example Table 2-1 1 2 3 4 5 6 7Liquid Compound A1 40 40 A Compound A2 40 Compound A3 40 Compound A4 40Compound A5 40 Compound A6 40 Glycidyl 50 50 50 50 50 50 50 compound B1Silane coupling agent Compound C1 10 (7) 10 (7) 10 (7) 10 (7) 10 (7) 10(7) 10 (7) Imidazolesilane 7 7 7 7 7 7 Catalyst 5 5 5 5 5 5 Liquid Water5 5 5 5 5 5 B Imidazole 10 compound D1 Pull-in amount [nm] 30.4 42.548.3 27.1 32.5 40.3 18.1 Working Working Working Working WorkingComparative Comparative Example Example Example Example Example ExampleExample Table 2-1 8 9 10 11 12 1 2 Liquid Compound A1 A Compound A2 40Compound A3 40 Compound A4 40 40 Compound A5 40 40 Compound A6 40Glycidyl 50 50 50 50 50 50 50 compound B1 Silane coupling 10 agentCompound C1 10 (7) 10 (7) 10 (7) 10 (7) 10 (7) Imidazolesilane 7Catalyst 5 Liquid Water 5 B Imidazole 10 10 10 10 10 10 compound D1Pull-in amount [nm] 21.8 35.3 16.3 20.3 32.5 82.3 70.4

TABLE 4 Working Working Working Working Working Comparative ComparativeTable 2-2 Example 8 Example 9 Example 10 Example 11 Example 12 Example 1Example 2 Liquid Compound A1 A Compound A2 40 Compound A3 40 Compound A440 40 Compound A5 40 40 Compound A6 40 Glycidyl compound B1 50 50 50 5050 50 50 Silane coupling agent 10 Compound C1 10 10 10 10 10 (7) (7) (7)(7) (7) Imidazolesilane 7 Catalyst 5 Liquid Water 5 B Imidazole compoundD1 10 10 10 10 10 10 Pull-in amount [nm] 21.8 35.3 16.3 20.3 32.5 82.370.4

The components listed in Table 2 are described below.

-   -   Compound A1: Compound A1 synthesized as described above    -   Compound A2: Compound A2 synthesized as described above    -   Compound A3: Compound A3 synthesized as described above    -   Compound A4: Compound A4 synthesized as described above    -   Compound A5: Compound A5 synthesized as described above    -   Compound A6: Compound A6 synthesized as described above    -   Glycidyl compound B1: MY-0510 (triglycidyl-p-aminophenol,        manufactured by Huntsman Advanced Materials) (The structure is        illustrated below)

-   -   Silane coupling agent: A187 (3-glycidoxypropyltrimethoxysilane,        manufactured by Momentive Performance Materials Inc.) (The        structure is illustrated below)

-   -   Compound C1: Compound C1 synthesized as described above    -   Imidazolesilane: IM-1000 (manufactured by JX Nippon Mining &        Metals Corp.)

-   -   Catalyst: TPT-100 (tetrapropoxytitanium, manufactured by Nippon        Soda Co., Ltd.)    -   Water    -   Imidazole compound D1: 1B2MZ (1-benzyl-2-methylimidazole,        manufactured by Shikoku Chemicals Corporation) (The structure is        illustrated below; Me represents a methyl group and Bz        represents a benzyl group)

As is clear from Table 2, the adhesive compositions of Working Examples1 to 12, which contained the compound (C) having a silsesquioxane cagestructure resulted in lower pull-in amount compared to the adhesivecompositions of Comparative Examples 1 and 2, which contained nocompound (C) having a silsesquioxane cage structure. In particular,Working Examples 7 to 12, in which an imidazole compound (D) was furthercontained and the imidazole compound (D) was the compound represented byFormula (4) above and R₄₃ in the Formula (4) was an alkyl group, tendedto have even lower pull-in amount.

From the comparison of Working Examples 1 and 4, Working Example 4, inwhich the number of equivalent of active hydrogen in the amino group orthe imino group was 0.6 equivalent or greater relative to the amount ofepoxy group contained in the epoxy compound (e), resulted in even lowerpull-in amount. Similarly, from the comparison of Working Examples 2 and5, comparison of Working Examples 3 and 6, comparison of WorkingExamples 7 and 10, comparison of Working Examples 8 and 11, andcomparison of Working Examples 9 and 12, Working Examples 5, 6, 10, 11,and 12, in which the number of equivalent of active hydrogen in theamino group or the imino group was 0.6 equivalent or greater relative tothe amount of epoxy group contained in the epoxy compound (e), resultedin even lower pull-in amounts.

REFERENCE SIGNS LIST

-   1 Optical fiber-   2 Core part-   3 Cladding part-   4 Polymer coating layer-   6 Adhesive layer-   7 Ferrule-   8 Flange-   10 Connector

The invention claimed is:
 1. An adhesive composition for a high-poweroptical fiber comprising: a compound (A) having an aromatic ring and areactive silicon-containing group; a glycidyl compound (B); and acompound (C) having a silsesquioxane cage structure, wherein aproportion (A/(A+B+C)) of a content of the compound (A) in a totalcontent (A+B+C) of the content of the compound (A), a content of theglycidyl compound (B), and a content of the compound (C) is from 20 to70 mass %; a proportion (B/(A+B+C)) of the content of the glycidylcompound (B) in the total content (A+B+C) is from 20 to 70 mass %; and aproportion (C/(A+B+C)) of the content of the compound (C) in the totalcontent (A+B+C) is from 5 to 40 mass %.
 2. The adhesive composition fora high-power optical fiber according to claim 1, further comprising animidazole compound (D).
 3. The adhesive composition for a high-poweroptical fiber according to claim 1, wherein the reactivesilicon-containing group is a hydrolyzable silicon-containing group. 4.The adhesive composition for a high-power optical fiber according toclaim 1, wherein the compound (A) is obtained by reacting an epoxycompound (e) with a compound (f) having a reactive group that reactswith the epoxy group contained in the epoxy compound (e).
 5. Theadhesive composition for a high-power optical fiber according to claim4, wherein the epoxy compound (e) is an aromatic epoxy compound, and thecompound (f) is an iminosilane compound.
 6. The adhesive composition fora high-power optical fiber according to claim 4, wherein the epoxycompound (e) is an epoxysilane compound, and the compound (f) is anaromatic amine compound.
 7. The adhesive composition for a high-poweroptical fiber according to claim 4, wherein the compound (f) has anamino group or an imino group, and the number of equivalent of activehydrogen in the amino group or the imino group is from 0.1 to 1.0equivalent relative to the amount of epoxy group contained in the epoxycompound (e).
 8. The adhesive composition for a high-power optical fiberaccording to claim 1, wherein the compound (C) is obtained by subjectingat least one type of silane selected from the group consisting ofepoxysilane, aminosilane, vinylsilane, methacrylsilane, acrylsilane, andmercaptosilane to condensation.
 9. The adhesive composition for ahigh-power optical fiber according to claim 2, wherein the reactivesilicon-containing group is a hydrolyzable silicon-containing group. 10.The adhesive composition for a high-power optical fiber according toclaim 2, wherein the compound (A) is obtained by reacting an epoxycompound (e) with a compound (f) having a reactive group that reactswith the epoxy group contained in the epoxy compound (e).
 11. Theadhesive composition for a high-power optical fiber according to claim3, wherein the compound (A) is obtained by reacting an epoxy compound(e) with a compound (f) having a reactive group that reacts with theepoxy group contained in the epoxy compound (e).
 12. The adhesivecomposition for a high-power optical fiber according to claim 9, whereinthe compound (A) is obtained by reacting an epoxy compound (e) with acompound (f) having a reactive group that reacts with the epoxy groupcontained in the epoxy compound (e).
 13. The adhesive composition for ahigh-power optical fiber according to claim 5, wherein the compound (f)has an amino group or an imino group, and the number of equivalent ofactive hydrogen in the amino group or the imino group is from 0.1 to 1.0equivalent relative to the amount of epoxy group contained in the epoxycompound (e).
 14. The adhesive composition for a high-power opticalfiber according to claim 6, wherein the compound (f) has an amino groupor an imino group, and the number of equivalent of active hydrogen inthe amino group or the imino group is from 0.1 to 1.0 equivalentrelative to the amount of epoxy group contained in the epoxy compound(e).
 15. The adhesive composition for a high-power optical fiberaccording to claim 2, wherein the compound (C) is obtained by subjectingat least one type of silane selected from the group consisting ofepoxysilane, aminosilane, vinylsilane, methacrylsilane, acrylsilane, andmercaptosilane to condensation.
 16. The adhesive composition for ahigh-power optical fiber according to claim 3, wherein the compound (C)is obtained by subjecting at least one type of silane selected from thegroup consisting of epoxysilane, aminosilane, vinylsilane,methacrylsilane, acrylsilane, and mercaptosilane to condensation. 17.The adhesive composition for a high-power optical fiber according toclaim 4, wherein the compound (C) is obtained by subjecting at least onetype of silane selected from the group consisting of epoxysilane,aminosilane, vinylsilane, methacrylsilane, acrylsilane, andmercaptosilane to condensation.
 18. The adhesive composition for ahigh-power optical fiber according to claim 5, wherein the compound (C)is obtained by subjecting at least one type of silane selected from thegroup consisting of epoxysilane, aminosilane, vinylsilane,methacrylsilane, acrylsilane, and mercaptosilane to condensation. 19.The adhesive composition for a high-power optical fiber according toclaim 6, wherein the compound (C) is obtained by subjecting at least onetype of silane selected from the group consisting of epoxysilane,aminosilane, vinylsilane, methacrylsilane, acrylsilane, andmercaptosilane to condensation.